The present invention is related generally to the field of orthodontics. Particularly, this invention relates to the use of removable orthodontic appliances for producing tooth movements. More particularly, this invention relates to improved devices, systems and methods for producing such tooth movements with elastic repositioning appliances.
Orthodontic treatments involve repositioning misaligned teeth and bite configurations for improved cosmetic appearance and dental function. Repositioning teeth is accomplished by applying controlled forces to the teeth over an extended period of time. This is conventionally accomplished by wearing what are commonly referred to as xe2x80x9cbraces.xe2x80x9d Braces are typically comprised of brackets or bands which are bonded to the teeth and linked with the use of archwires, ligatures and O-rings. After the archwire is in place, periodic appointments with the orthodontist are required, during which the patient""s braces will be adjusted. This involves installing different archwires having different force-inducing properties or by replacing or tightening existing ligatures. Between meetings, the patient may be required to wear supplementary appliances, such as elastic bands or headgear, to supply additional or extraoral forces.
Although conventional braces are effective, they are often a tedious and time consuming process requiring many visits to the orthodontists office. Moreover, from a patient""s perspective, they are unsightly and uncomfortable. The archwire and ligatures which connect the brackets in a continuous network make brushing, flossing between the teeth and other dental hygiene procedures difficult, possibly contributing to the development of gingivitis, caries, and other dental disease. Consequently, alternative orthodontic treatments are needed. In particular, it would be desirable to use appliances which can be removed by the patient during daily dental hygiene routines, while participating in athletic activities, or for cosmetic purposes.
A particularly promising approach relies on the use of elastic positioning appliances for realigning teeth. Such appliances comprise a thin shell of elastic material that generally conforms to a patient""s teeth but is slightly out of alignment with the initial tooth configuration. Placement of the elastic positioner over the teeth applies controlled forces in specific locations to gradually move the teeth into the new configuration. Repetition of this process with successive appliances comprising new configurations eventually move the teeth through a series of intermediate configurations to a final desired configuration. A full description of an exemplary elastic polymeric positioning appliance is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present invention. Both documents are incorporated by reference for all purposes.
In addition to their ease of use, polymeric positioning appliances are generally transparent, providing an improved cosmetic appearance, and impart substantial force on the teeth, due to stiffness of the appliance. The stiffiess of an elastic positioning appliance is a result of the modulus of the thermoformable polymer materials from which it is made. The higher the modulus of the materials, the higher the stiffness of the appliance. By designing the appliance to cover the teeth, a much larger and/or more varied contact surface area may be afforded compared to traditional spring retainers and wire-based appliances. Consequently, more dramatic tooth movements may be achieved.
In some cases, however, orthodontic treatment may involve more complex tooth movements or treatment plans requiring additional devices or accessories. For example, it may be desirable to apply forces to surfaces of the teeth that may not be easily achieved by the appliance alone, either due to the location or characteristics of the surface itself or of the surrounding teeth. Similarly, it may be desirable to apply extraoral forces to some tooth surfaces to achieve certain tooth movements or to control growth and development of the bite and jaws. Likewise, it may be desirable to achieve such control indirectly through soft tissue stretch and muscular activity. Alternatively, it may be preferable to allow the passive eruption and movement of certain teeth, free of applied forces. The devices and accessories commonly utilized for these situations are typically separate removable appliances worn prior to the application of conventional braces, or accessories used in conjunction with conventional braces. Thus, such devices and accessories may not be compatible with the use of elastic polymeric positioning appliances for orthodontic treatment.
Consequently, improved methods and apparatus for achieving these treatment objectives are desired for complete orthodontic treatment in such patients. Such devices, systems and methods would maintain the advantages of and be compatible with a removable appliance while providing supplementary features to assist in the improvement of jaw structuring, alignment and tooth repositioning, to name a few. At least some of these objectives will be met by the designs and methods of the present invention described hereinafter.
The present invention provides improved devices, systems and methods for repositioning teeth from a first orientation to a successive orientation in a series of movements to a final tooth and bite configuration. Such repositioning is based on a system comprising at least one and usually a plurality of three or more elastic repositioning appliances configured to receive the teeth in a cavity and incrementally reposition individual teeth, usually in a series of successive steps. In cases involving more complex movements or treatment plans, it may be desired to utilize additional devices, components or accessories. The present invention provides for the utilization of such devices, components or accessories typically used in conventional orthodontic treatment. In some instances the present invention provides improved elastic repositioning appliances that take the place of such additional accessories. Further, the present invention may provide improved elastic repositioning appliances that provide simultaneous repositioning of tooth and bite configurations that may be unachievable with conventional devices.
In a first aspect of the present invention, a removable elastic positioning appliance, typically used in a series of successive elastic appliances for orthodontic treatment, may be comprised of a polymeric shell having at least one orthodontic component or accessory. These components or accessories may be independent entities that are embedded in the polymeric shell during production of the appliance. Or, they may be mounted on the polymeric shell with a suitable adhesive in a post-production assembly protocol. In either case, the components may be traditional accessories that are typically used with conventional orthodontic devices, such as braces, or they may be any other readily available components used for dental treatment. Alternatively, the components may be specially created accessories designed for specific purposes when used with removable elastic positioning appliances. Such specially created accessories may be independent entities present on or in the polymeric shell as described above, or they may be formed by the polymeric shell itself. In these cases, the component may be a formed protrusion or shape in the wall of the polymeric shell, providing a variety of advantages, including but not limited to increased stability, safety from breakage, ease of manufacturing, cost savings, shortened treatment time and improved cosmetic appearance and patient compliance.
In a first embodiment, the orthodontic components or accessories may be conventional accessories typically used with fixed, non-removable orthodontic devices. For example, headgear tubes are conventional accessories typically mounted on traditional braces for inserting a headgear device and applying extraoral force to the teeth and jaws. Tubes for receiving headgear may be mounted on or embedded in the polymeric shell of an elastic positioning appliance for a similar effect. Similarly, orthodontic hooks may be mounted on traditional braces to support elastic bands which may also apply distinct forces to the teeth and jaws. As with headgear tubes, such hooks may also be mounted on or embedded in the polymeric shell of a positioning appliance for a similar effect. Likewise, a number of other conventional accessories, such as brackets, springs, bumper tubes, palatal bars, frameworks, pin-and-tube apparatuses and the like, may be used in conjunction with polymeric positioning appliances. In some cases, such as with brackets, the accessory may be used to join a removable elastic appliance with a portion of teeth supporting fixed conventional devices, such as braces.
In a second embodiment, the orthodontic components or accessories may be those which are primarily exclusive to removable appliances. These components are not generally suited for use with fixed appliances and devices due to their bulk and size. In addition, they are often used prior to the use of fixed devices to create a favorable environment for later tooth repositioning. For example, when a patient""s teeth are still erupting, a number of devices may be used to foster improved eruption and development of the tooth arrangement and bite configuration. These may include buccal shields, buccinator bows or wire shields, bite plates, palatal expanders and bars, lingual flanges and pads, lip pads or bumpers, and the like. Since these components are currently used with removable appliances, they are ideally suited for use with removable elastic positioning appliances. Thus, the components may be mounted on or embedded in the polymeric shell of an elastic appliance. Similarly supporting structures for such components may also be mounted or embedded in the polymeric shell for the removable application of a component. For example, a bumper tube may be embedded in the polymeric shell for later insertion and removal of a bumper. Alternatively, the components may be formed by the appliance itself, such components comprising a formed protrusion or shape in the wall of the polymeric shell. In these cases, the elastic repositioning appliance may take the place of any additional accessories.
An added advantage of the use of elastic repositioning appliances having these components or accessories is the ability to provide the conventional benefit of the accessory while simultaneously repositioning the teeth, a combination previously limited. In conventional treatment, the use of fixed devices to reposition the teeth negated the ability of simultaneously using accessories provided by some removable appliances since removable appliances may not be readily applied with fixed devices in place. For example, situations in which it is desired to control eruption of specific teeth concomitant with repositioning of the same or other teeth would cause great difficulty if not an impossible dilemma with traditional devices. The present invention may provide such simultaneous maneuvers which are unachievable with conventional treatment.
In a second aspect of the present invention, a removable dental positioning appliance, typically used in a series of successive elastic appliances for orthodontic treatment, may be comprised of at least one protrusion shaped to be used for an orthodontic function. As described above, such a protrusion may resemble, in form or function, a traditional component or accessory used in conventional orthodontic treatment with fixed, non-removable devices or with removable appliances. For example, an appliance may have a protrusion or shape in the wall of the polymeric shell in the form of a hook for mounting flexible bands, ligatures or adjunct devices. Such a hook may resemble traditional hooks found in dental care, or it may be specially designed for use with elastic repositioning appliances. Likewise, such a protrusion may form a spring which transmits force to one or more teeth to reposition teeth from a first arrangement to a successive arrangement. A spring of this type may be of a traditional design or it may be specially designed for use with elastic repositioning appliances. Further, it may be specially designed to engage an attachment body mounted on a tooth, a device primarily utilized in conjunction with removable elastic appliances. A full description of exemplary attachment bodies and devices is described in published PCT application WO 99/28228, which corresponds to co-pending application Ser. No. 09/454278, assigned to the assignee of the present invention. Both documents are incorporated by reference for all purposes. Thus, in these and similar cases, such as a palatal bar, the protrusion may take the place of a traditional accessory or component, or it may be utilized in a specialized manner.
In one embodiment, the protrusion may contact one or more dental surfaces to assist in holding the elastic appliance in position. For example, one or more protrusions may be sized and located to contact interdental areas of the patient""s teeth, often near the gingival margin, when the appliance is properly inserted and positioned. Such protrusions may be formed in the wall of the polymeric shell, or they may be adhered to or embedded into the polymeric shell to protrude from the wall. Such placement of the protrusions may provide additional friction and xe2x80x9cgrabxe2x80x9d in dental regions conducive to this effect. Similarly, a protrusion may be sized and located to contact a tooth along a portion of the gingival margin, with or without contact in the interdental areas. Or, the protrusion may be a continuous protrusion contacting more than one tooth along the gingival margin and the interdental areas. In each of these cases, the contact of the protrusion may assist in holding the appliance in proper position.
In another embodiment, the one or more protrusions may form a bite plate. A bite plate is a device which prevents the teeth from closing completely. By opening the bite in this manner, unopposed teeth may be allowed to passively erupt in a controlled manner to beneficially alter vertical dental relationships. In addition, such an open state or disclusion may relieve teeth which are in crossbite allowing orthodontic forces to correct the crossbite.
To provide anterior disclusion, an elastic positioning appliance may have an increase in thickness of material in the posterior occlusal regions. This increase in thickness may be applied to the appliance or formed by the appliance to create a protrusion over the designated occluding surfaces. Similarly, posterior disclusions may be provided by forming a protrusion which extends at least a portion of an upper palatal region with added thickness. Alternatively, posterior disclusions may be provided by forming a protrusion in an upper lingual or lower facial anterior region. Such protrusions may prevent the front teeth from closing completely, thus discluding the posterior teeth. As previously described, such protrusions may be formed in the appliance or applied to the surface of the appliance.
Such embodiments of the present invention may be utilized in the treatment of patients with a condition commonly termed a xe2x80x9cdeep bitexe2x80x9d. In these cases, the lower teeth contact the upper teeth and/or the palate in the natural bite. This occurs when the posterior teeth are not fully erupted in the correct position allowing the anterior teeth to become overdosed or overlap more than is desirable. Such a bite is injurious to the palate, tends to crowd the lower teeth, and affects flaring of the upper teeth leading to upper spaces. This may be alleviated with the use of a bite plate which provides posterior disclusion. Such disclusion allows the posterior teeth to naturally erupt without contacting the opposing teeth which may impede their eruption into the correct position. The present invention may provide the function of a bite plate while additionally providing repositioning forces and other orthodontic treatment to the patient. These functions may be simultaneous, an attribute not previously afforded by conventional orthodontic treatment.
In a third aspect of the present invention, a removable dental positioning appliance, typically used in a series of successive elastic appliances for orthodontic treatment, may be comprised of at least one space filler shaped to align with a gap between adjacent teeth. If a tooth is extracted from a patient""s dentition, a space or gap will be left behind between adjacent teeth. A similar gap may also be present due to general misalignment of the teeth. An elastic positioning appliance may be made to be positioned over a gap and its surrounding teeth. In such a case, a space filler may be shaped to align with the gap. In a preferred embodiment, the space filler may be a cavity in the polymer shell having the shape of at least a portion of a tooth, dental feature, sphere, oval or three-dimensional curved and/or flat sided object. In the case of a tooth shape, the space filler may act as a xe2x80x9cpontic,xe2x80x9d a fake tooth placed where a tooth is missing to give the appearance of the presence of a tooth. This same effect may also be given by other shapes. Likewise, as a gap is gradually eliminated due to repositioning of the teeth, a variety of shapes may be suitable throughout the repositioning process.
To further conceal the presence of a space or gap between teeth during orthodontic treatment, a space filler may be opacified. By making the space filler at least partially opaque, it may give a more convincing appearance of the presence of a tooth or dental feature. Such opacity may be an effect of surface treatment of the space filler. For example, the inside and/or outside surfaces of the space filler may be painted with a tooth-colored material. Alternatively, the surfaces may be microetched to give a more frosted appearance to the polymeric shell material. In either case, the space or gap may be less visible.
In addition to improving cosmetic appearance, a space filler may also provide structural support for the elastic appliance. When a space filler is a cavity, as described above, the presence of the cavity improves the structural integrity of the appliance by providing a uniform geometry. Alternatively, a space filler may be any number of structures providing similar support. For example, a space filler may be a structure that is at least partially solid. This may be achieved by the formation of a solid section of material spanning the gap, similar to a bridge or slab between adjacent teeth. Such a solid section may be formed by the fusing of the walls of the polymeric shell together. Alternatively, the shell may be filled with a solid material. In this case, the shell may be designed with undercuts or prongs to retain the solid material. In addition, a solid section may be corrugated to additionally improve the integrity of the appliance.
In a fourth aspect of the present invention, a removable dental positioning appliance, typically used in a series of successive elastic appliances for orthodontic treatment, may be comprised of a polymeric shell having cavities shaped to receive and reposition teeth, wherein one or more cavities has a window to expose at least a portion of a received tooth. Such windows may be portions of the wall of the polymer shell which are removed. When the shell is positioned over the patient""s teeth, portions of the teeth beneath the windows may be exposed. Exposing such tooth surfaces may allow brackets, buttons or other orthodontic components to be utilized in conjunction with the elastic appliance or to be exposed for other purposes.
In a preferred embodiment, a polymeric shell may have a plurality of windows over portions of the occlusal surfaces of the teeth. In this case, segments of the shell may still be present along the facial and lingual surfaces of the teeth and across the interdental regions or spaces between the teeth. Exposure of the occlusal surfaces in appropriate size and location may allow interdigitation of the upper and lower teeth. This may also be achieved with the presence of one or a few larger windows over portions of the occlusal surfaces of the teeth. In these cases, segments of the shell may not be present across the interdental regions or spaces between the teeth. In either case, interdigitation of at least portions of the upper and lower teeth may benefit tooth and jaw orientations, leading to improved treatment, appearance, comfort and consequently patient compliance. Likewise, similarly placed windows may provide the benefits offered by a lower elastic modulus, such that the lowest stiffness may be provided by the absence of the material. Such benefits and a full description is provided in co-pending application Ser. No. 09/616,830, assigned to the assignee of the present invention.